Brake problem - Master cylinder?

Just to add to what i said previously, so as not to waste too much of your time. I did remove the switch from the master when bleeding. The plastic thread is slightly stripped, but sitch sits in place when screwed back in. I bleed them in the following order. Far Rear, Near Rear, Far Front, Near Front.

It's possible that there is something wrong with the pressure differential valve that you couldn't remove. It could be frozen. It's hard to say but let's assume that it's ok.

The tandem master cylinders are very difficult to bleed. They will retain air quite easily. The best procedure is to bench bleed the cylinder but you can do something similar with the master cylinder in the car. You will need to make some outlet tubes that are short versions of the normal outlets, maybe 2 or 3 cm. long tubing. To these short pieces of metal tubing attach pieces of clear plastic tubing and route them into the fluid reservoir. The ends of these tubes should almost reach the bottom of the reservoir. With all this assembled pump the pedal slowly until all of the air bubbles disappears from the tubes. This can take a long time so be patient.

When your sure the master cylinder is free of air reconnect the brake lines and bleed the system. The order you have listed appears correct.

Good luck,

Cheers,

Kelley

A little trick you might like to try; it's worked for me. Pump the brake pedal until it's as hard as you can get it, then use a block of wood or similar to wedge it down overnight. It costs nothing and can't hurt to try! Seems it forces the air to the highest point, ie the master cylinder reservoir.

One other thing to check as that your drum brakes are adjusted properly as this will affect pedal travel. You might also want to look over the calipers on the front brakes (assuming you have them), I have had rust on the anti squeal shims that have caused similar problems to that described.

-anthony

hi agree with all the replies you have but would think a new master cylinder is in order if non of those things work i dont have a lot of faith in the seal kit hard to tell if the bore is spot on hope you sort it

"angelon" wrote: > Hi, please help w.r.t. a brake problem thats been around for > ages > although I believe the cause has been changing. > My 1275HLE Clubman 1982 has a tandem type master cylinder with > a front/ > back split. What Haynes calls "Later" version. > > Symptom: pedal goes all the way to the floor the first time. > Even > pumping once raises the pedal height giving me good brakes > once only. > > Each time after bleeding (done this countless times with auto > kit and > manually following Haynes instructions) the pedal "comes" up > but > eventually fades after few brake tests. > > I had leaks at some wheels but have fixed this by replacing > most > cylinders. > I had the carpet leak and bought a master cylinder kit but was > only > able to replace the main seals. > I was not able to remove the smaller piston where Haynes > simply says > remove big hexagonal screw and take out piston. > I removed the screw, but the piston wouldn't come out. Could > it be > siezed or is there some trick. I didn't see any "stop pin" > like the > one on the main. > Could this be my problem or am I barking up the wrong tree? > > Pleeaaaase help me someone. > > Tks. in advance. - Angelo (Black 1275HLE 1982)

As has been suggested check the adjustments in the rear brakes or get a new set of drums.

Not a new M/C.

rm